Re: Exclusive Unix file system file write locks and Oracle and Veritas

Could you Pls Clarify the statement ' writers lock Readers and readers lock writers on the inode level in UFS ' ?

UFS uses File Buffer Cache which provides Read Consistent Data(similar to ORacle) and they dont lock the entire Inode..

-Thiru

Jonathan Lewis wrote:

> Under Unix file system, writers lock readers and readers lock
> writers independently of anything that Oracle is doing. The
> lock is on the inode to ensure that a read cannot read data
> that is changing.
>
> This also happens under Veritas, but the nature of vxfs makes
> the lock (usually) a little shorter. Also the latest version of
> veritas has further optimisation in it for 'quick db' which I think
> helps further.
>
> The main benefit for 'small files' is in mixing parallel query
> and TEMP. If you run create index in parallel, then all the
> query slaves are likely to be reading and writing to TEMP
> at the same time and interfering at the O/S level, so it
> is better to have N files in temp matching the degree of
> parallelism to reduce the probability of O/S collisions.
>
> (This is the extreme case of course, but the same idea
> holds any tablespace which is likely to be subject to
> large numbers of concurrent reads and writes - Rollback
> segment tablespaces are __likely__ to be the next
> candidate on busy systems).
>
> --
>
> Jonathan Lewis
> Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk
>
> NetComrade wrote in message <37d93dab.269121198_at_news.earthlink.net>...
> >What I really meant, what are the UNIX constraints on Oracle (or
> >should I say veritas constraints), since theoretically on a UFS there
> >are locks placed on a file upon writes. DOes Veritas do the same
> >thing? As for Oracle locking, I really don't have any on any of my
> >machines, expect for some MR locks, which are constantly there, and I
> >don't really know what they mean, but they are placed by PMON, so it
> >must be cleaning up something.
> >
Received on Fri Sep 10 1999 - 14:05:45 CDT